Sir Paul McCartney, the most successful musician in pop history, returns to court today to try to reach a settlement over his failed marriage.

The former Beatle faces his estranged wife, Heather Mills, across a courtroom where they will be battling over money and access to their child after a marriage that lasted less than four years.

He married Mills in June 2002 just four years after his first wife, Linda, died of breast cancer.

Sir Paul, with 60 gold discs and 100 million singles sales, has a personal fortune estimated at £825 million - putting him at risk of facing the biggest payout in British legal history.

But unless one of the McCartneys takes issue with the settlement being hammered out behind closed doors in the Family Division of the High Court and goes to the Court of Appeal, the figures and details will never be known to the outside world.

There has been speculation among divorce experts, based on recent big money cases, that the settlement could reach £60 million. This would exceed the record £48 million businessman John Charman was told by the courts to pay his former wife in May last year.

But lawyers agree there are many imponderables which could limit Mills’ payout, including the shortness of the marriage and fact that the bulk of Sir Paul’s fortune was amassed decades before the couple met - she is just 40 while he will be 66 this year.

They have a three-year-old daughter, Beatrice, whose future will also figure large in the negotiations.

Suzanne Kingston, a family law expert, said: “Current estimates suggest that Heather is likely to receive anything from £50 to £100 million as her final settlement.

“In Heather and Sir Paul’s negotiations, making sure that their child Beatrice is properly provided for will be a key consideration, as will ensuring that there is not a vast disparity between Heather’s lifestyle and Paul’s as viewed by Beatrice.

“The fact that this has been a short marriage will be taken into account and this could involve looking at the wealth that has been generated during the course of the marriage as distinct from pre-marital wealth.”

The venue for the hearing is a cavernous, oak-panelled courtroom where the ceiling soars more than 30 ft.

It is in the West Green section of the Royal Courts of Justice - traditional home of divorce hearings before the advent of “quickie” divorces.

Back in the early part of the 20th century, the court division was called the Probate, Divorce and Admiralty - nicknamed Wills, Wives and Wrecks.

There was even provision for a jury, and large area for spectators because divorce hearings then were very public affairs.

But now the whole procedure is broken down into a hearing over the settlement - under the auspices of the Family Division where almost every case is held in private - and the divorce itself which is usually announced at a hearing lasting just seconds.

The only divorces held in public are those where the grounds for the split are contested.

The hearing, before Mr Justice Bennett and expected to last all week, concerns the financial aspects of the divorce and will be a very private affair.

It is being listed as a continuation of various earlier hearings at the High Court where attempts to reach a settlement were unsuccessful.